18 February 2009

Battery Revolution

I've realized recently that a number of my "guy stuff" interests (watches, DAPs, pocket knives) fit under the general umbrella of everyday carry items (EDC, in guy stuff lingo). A surprising number of guys give a surprising amount of thought to what they put in their pockets, on their key chains, and in their backpacks, briefcases, etc. It may be partly some hardwired Boy Scout impulse, but it makes sense that we should think hard about the stuff we pack everywhere with us.

So I ordered a mini flashlight. Any number of times I've wished I had one (again just last night), and with the incredible new LED emitters out now, a single AA flashlight just a little larger than the battery powering it can throw out an amazing amount of light for more than an hour. When I get it, I'll review it.

But another interesting discovery was that there has been a big leap in rechargeable battery technology in the last couple of years. I think it started in 2006, when Sanyo introduced their Eneloop batteries. You can read their website for details, but these are a fantastic improvement over older NiMH rechargeables. The biggest advance is this: Traditional NiMH cells discharge even when not in use (self-discharge). That means, if you charge them up and toss them in your camera, when you pull it out next month to use it, the batteries will be partly or even entirely dead. You basically have to charge them right before use.

But Eneloops retain 85% of their charge after a full year of storage. This is not as good as quality alkaline or (especially) lithium single-use cells, but it is still a phenomenal advance. And these cells still retain the two big advantages of traditional rechargeables: very high capacities (2000 mAh vs 400-1000 mAh for standard alkalines) and high reusability. Eneloops are said to be good for 1000 charge cycles. That means if you use a full charge and recharge every week, a set will last you 19 years.

How expensive are they? A four-pack of AAs is about $12. You can buy an excellent Duracell charger with two AAs from Amazon for $17. Given the cost savings, greater performance, and environmental benefits, there is now no reason to buy conventional alkalines. However, lithium cells are still the best choice for long-term emergency storage and extreme temperature usage. They self-discharge just 0.5% per year at room temperature, meaning they are still pretty fresh after 10 years, and work well even in very cold weather. They are also very energy dense (typically 2900 mAh for lithium AAs).

Since Eneloops came on the market, other manufacturers have introduced similar cells under the name "hybrid" or "pre-charged rechargeable." (Older rechargeables necessarily came uncharged.) The main contenders are Duracell Pre-charged Rechargeables, Rayovac Hybrids, and Kodak Pre-charged. Some Duracells (made in Japan) are thought to be rebranded Sanyo Eneloops, while other Duracells (made in China) are thought to be rebranded Rayovac Hybrids.They all perform similarly, but the Sanyos have a bit more energy than the Rayovacs.

Addendum: See updates here and here.

No comments: